1. Field of the Invention
This invention relates in general to equipment for pumping cuttings generated from drilling a subsea well back into another subsea well, and in particular to an adapter that connects an injection line to the inner wellhead housing.
2. Description of the Prior Art
When a subsea well is drilled, cuttings, which are small chips and pieces of various earth formations, will be circulated upward in the drilling mud to the drilling vessel. These cuttings are separated from the drilling mud and the drilling mud is pumped back into the well, maintaining continuous circulation while drilling. The cuttings in the past have been dumped back into the sea.
While such practice is acceptable for use with water based drilling muds, oil based drilling muds have advantages in some earth formations. The cuttings would be contaminated with the oil, which would result in pollution if dumped back into the sea. As a result, environmental regulations now prohibit the dumping into the sea cuttings produced with oil based drilling mud.
There have been various proposals to dispose of the oil base cuttings. One proposal is to inject the cuttings back into a well. The well could be the well that is being drilled, or the well could be an adjacent subsea well. Various proposals in patents suggest pumping the cuttings down an annulus between two sets of casing into an annular space in the well that has a porous formation. The cuttings would be ground up into a slurry and injected into the porous earth formation. Subsequently, the well receiving the injected cuttings would be completed into a production well.
U.S. Pat. No. 5,085,277, Feb. 4, 1992, Hans P. Hopper, shows equipment for injecting cuttings into an annulus surrounding casing. The equipment utilizes piping through the template or guide base and through ports in specially constructed inner and outer wellhead housings. Orientation of the inner wellhead housing with the outer wellhead housing is required to align the ports. In the '277 patent, orientation is not discussed, but it appears that it would require rotating the string of casing attached to the inner wellhead housing, which would be difficult. Another known injection system avoids having to rotate the string of casing attached to the inner wellhead housing by running the casing first, supporting it on a landing ring, then in a second trip running the inner wellhead housing assembly. The inner wellhead assembly has a port which is oriented. Then the inner wellhead assembly is secured to the string of casing. While workable, this requires two trips to run the inner wellhead housing and string of casing, which is time consuming for deep water drilling.